1. Field of the Present Invention
The present invention generally relates to the field of network computing and more particularly to a method and system for reducing energy consumption in a server cluster by dynamically adjusting the operating frequency of selected server-network links.
2. History of Related Art
In the field of networked computing and data processing, server clusters are commonly used as a means of providing network services. A server cluster typically includes a set of server devices, each of which is capable of processing server requests. The cluster may include a request distributor that is configured to route incoming requests to an appropriate server in the server cluster for processing. Requests may be distributed to the individual servers based upon the current loading of the individual servers, the origin of the request, the location of the requested file or data, or other appropriate factors.
Server clusters are frequently arranged according to a switched configuration in which each server communicates with a central switch via a transmission medium such as twisted copper, fiber optic cable, or wirelessly transmitted electromagnetic waves. When the network parameters are configured, a transmission rate is established for each server-switch link based upon the bandwidth capabilities of the respective network interface cards and the transmission medium itself. Typically, the transmission rate for a given link is determined when the link is established and remains set during the link lifetime. Moreover, the transmission rate that is established is typically the highest possible transmission rate that both ends of the link can accommodate.
Maintaining the transmission rate of each network link at the highest possible value maximizes performance but only at the cost of increased power consumption. It is common knowledge that operating a network link at high frequency costs more than operating the same link at low frequency. Moreover, the additional cost incurred to operate the network links at high frequency often does not translate into correspondingly improved performance because the data transmission rate may be limited by factors other than the physical bandwidth of the link between the server and switch.
The sum of the bandwidth of the individual server-switch links cannot exceed the bandwidth allocated to the server cluster as a whole. Thus, if a server cluster having an allocated bandwidth of 200 Megabits/second (Mbps) is supporting a total of 20 servers, each connected to a central switch with a 100 Mbps link, it is physically impossible for all of the links to operate at their maximum bandwidth simultaneously. Moreover, the connection between a remote client and the server cluster may represent a limit on the usable bandwidth of the server-switch link. If a client connects to the server cluster (and an individual server) over a 56 Kbps modem connection during a period when there is no other network traffic, the maximum bandwidth of the server-switch link that can be utilized to service the client request is 56 K. If the server-switch link is operating at 100 Mbps as an example, the bandwidth will be severely underutilized. It would therefore, be desirable to implement a method and system for dynamically conserve energy consumption in a data processing network by dynamically optimizing the operating frequencies of the server links in response to changing network conditions.